Method for starting an internal combustion engine, particularly an internal combustion engine having direct fuel injection

Abstract

During a start, particularly during a cold start, of an internal combustion engine without additional auxiliary drive, a precisely metered fuel mass is introduced into a combustion chamber. In the case of an internal combustion engine having direct fuel injection, a rail pressure prevailing in a high-pressure accumulator is frequently only insufficiently built up during a start, which has an unfavorable effect on the mixture formation. To improve the start performance of the internal combustion engine, the injection pressure available in the high-pressure accumulator is monitored during the start, and fuel from the high-pressure accumulator is first injected into the at least one combustion chamber when the injection pressure has reached or exceeded a specifiable threshold value. This ensures that the rail pressure is high enough, in order to inject a sufficient quantity of fuel into the combustion chamber so that an ignitable air/fuel mixture is formed.

1. A method for starting an internal combustion engine, comprising:
 actuating a starter switch for the internal combustion engine;  
 after the starter switch is actuated, building up an injection pressure in a high-pressure accumulator of the internal combustion engine;  
 monitoring the injection pressure available in the high-pressure accumulator during the start; and  
 first injecting fuel from the high-pressure accumulator into at least one combustion chamber of the internal combustion chamber when the injection pressure has reached or exceeded a specifiable threshold value.  
 
   
   
     2. The method as recited in  claim 1 , further comprising:
 monitoring a time elapsed since the actuation of the starter switch, where the fuel is first injected into the at least one combustion chamber at the latest when the time has reached or exceeded a specifiable maximum waiting time.  
 
   
   
     3. The method as recited in  claim 2 , determining a duration of an injection during the start as a function of the pressure prevailing in the high-pressure accumulator. 
   
   
     4. The method as recited in  claim 1 , further comprising:
 activating an electrically actuatable presupply pump for building up the injection pressure in the high-pressure accumulator.  
 
   
   
     5. The method as recited in  claim 1 , wherein the buildup of the injection pressure in the high-pressure accumulator of the internal combustion engine is begun as a function of a driver-present signal. 
   
   
     6. The method as recited in  claim 5 , wherein the driver-present signal is generated by a door contact switch. 
   
   
     7. The method as recited in  claim 5 , wherein the driver-present signal is generated by a sensor for detecting occupancy of the driver's seat. 
   
   
     8. A control unit for at least one of controlling and regulating a high-pressure injection system of an internal combustion engine, comprising:
 an arrangement configured to monitor an injection pressure available in a high-pressure accumulator of the high-pressure injection system during a start of the internal combustion engine; and  
 an arrangement configured to first induce an injection of fuel from the high-pressure accumulator into at least one combustion chamber of the internal combustion engine when the injection pressure has reached or exceeded a specifiable threshold value.  
 
   
   
     9. The control unit as recited in  claim 8 , further comprising:
 an arrangement that monitors a time elapsed since the actuation of the starter switch, and induces an injection of fuel into the at least one combustion chamber at the latest when the time has reached or exceeded a specifiable maximum waiting time.  
 
   
   
     10. The control unit as recited in  claim 9 , further comprising:
 an arrangement configured to determine a duration of an injection during the start as a function of a pressure prevailing in the high-pressure accumulator.  
 
   
   
     11. A computer readable medium coded with a computer program that is executable on a computing element for causing the computing element to implement a method for starting an internal combustion engine when the computer program is executed by the computing element, the method comprising:
 actuating a starter switch for the internal combustion engine;  
 after the starter switch is actuated, building up an injection pressure in a high-pressure accumulator of the internal combustion engine;  
 monitoring the injection pressure available in the high-pressure accumulator during the start; and  
 first injecting fuel from the high-pressure accumulator into at least one combustion chamber of the internal combustion chamber when the injection pressure has reached or exceeded a specifiable threshold value.  
 
   
   
     12. The computer readable medium as recited in  claim 11 , wherein the medium is one of a RAM (random-access memory), ROM (read-only memory), or a flash memory. 
   
   
     13. A method for starting an internal combustion engine, comprising:
 actuating a starter switch for the internal combustion engine;  
 after the starter switch is actuated, building up an injection pressure in a high-pressure accumulator of the internal combustion engine;  
 monitoring the injection pressure available in the high-pressure accumulator during the start;  
 first injecting fuel from the high-pressure accumulator into at least one combustion chamber of the internal combustion chamber when the injection pressure has reached or exceeded a specifiable threshold value; and  
 determining a duration of an injection during the start as a function of the pressure prevailing in the high-pressure accumulator.  
 
   
   
     14. A control unit for at least one of controlling and regulating a high-pressure injection system of an internal combustion engine, comprising:
 an arrangement configured to monitor an injection pressure available in a high-pressure accumulator of the high-pressure injection system during a start of the internal combustion engine;  
 an arrangement configured to first induce an injection of fuel from the high-pressure accumulator into at least one combustion chamber of the internal combustion engine when the injection pressure has reached or exceeded a specifiable threshold value; and  
 an arrangement configured to determine a duration of an injection during the start as a function of a pressure prevailing in the high-pressure accumulator.